Voltage dividers are commonly installed across a comparatively high voltage source and tapped to afford availability of a fixed or variable fraction of the applied voltage. Typical passive voltage dividers of the prior art commonly utilize a resistor of high meg-ohm value calculated to produce the required voltage drop. Characteristically, such resistors are subject to stress effects which after many hours of use tend to decrease the original resistance value of the resistor to a nominal fraction thereof. When such resistor failure occurs, the output voltage of the divider increasingly approaches the value of the input voltage thereby defeating the purpose for which the voltage divider was provided. As can be appreciated, the foregoing can cause catastrophic failure of any peripheral devices which depend on a low voltage input from the voltage divider along with the interconnecting wire thereto.
One approach for contending with the above has been to provide a backup shunt circuit with protective components able to dissipate large amounts of power. To be effective, such components must be oversized, and by virtue of the leakage resistance and currents associated therewith the components are temperature sensitive as to render the attenuation factor of the voltage divider both temperature sensitive and unpredictable.
Despite recognition of the foregoing, a ready solution therefor has not previously been known.